Pbimary cell



June 12, 1928.

M. L. MARTUS ET AL PRIMARY CELL Filed Oct. 5, 1926 l! VVI|1||||||||||.coneau QSOoo:

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wwntom/ tbozlaq Patented June 12, 1928.

UNITED STATES PATENT OFFICE.

MARTIN L.' MARTUS, 10F WOODBURY, AND EDMUND H. BECXR, 0F WATERBUBY,

CONNECTICUT.

` PRIMARY CELL.

This` invention relates to priniarycells.; and il, comprises a primary cell utilizing the. principle of air depolarization, said cellconiprisiiuia positive eleiucnt such as VZinc, an allniliueelia-,trolyte such as caustic soda solution and a negative eleiiieiitofactivated carbon, said activated carbon eleinent ex` tendini;` abovethe norinal electrolyte level into contati with air, means to retardevap 'iiatiou of .said electrolyte con'iprising an oil la ver on thesurface of said electrolyte and rnifgans lo protect the carbon. eleinentfrom coinii'ig in contactvwith the oil layer; all as iiioi'e fullyhereinafter set forth and as claimed.

ltis the object of the present invention to provide a cell of an` airdepolarized'type having `great reliability on closed circuit, notsiibieirt to ilan'iage on open circuit, of ccoiioiiiical constructionand developing a hit/li voltage, ells under the present in'w veiii'ionwill leveling a steady voltage of 1.2i). ln accomplishing this result,advantage is 'taken ol' the property/'of a specially pre` pared pin-ouscarbon known as activated carbon of iulsorbing, holdinv' andtrai'isferring oxygen in an active state.

Most carboiis have the power of condensing and holding andr adsoi'binglayers of oxygen; a fact which has long been utilized iii theeiiiployuient of charcoal to taire up and dispose of offensive vaporsand in utilizing carbon for purifying liquids. Yarious propositions havebeen inade to utilize this property in depolariziiig p riinary cells; aresult niuch to be desired, both because of the economy of using aerialoxygen and because higher `voltages should be attained than are givenwith ordinary depolarizing materials, such `as copper oxid. Theseatteinpts however, for lvarious reasons, have not been successful` inproducing anything practical. (larbon is, of course, frequently used asa conductive eleinent iii making negative elements for priinary cells;but it is not itself relied `upon foil` any depolai'izing e'll'ect. Thecarbon` ordinarily employed in nerr Ative elements is,`as a matter offact, us ally not very reactive for any useful chemical purpose. Itspower of oxygen absorption, and particularly to the extent hereing;contemplated, .is negligible. Ordinary charcoal. for instance, is notsufficiently active because of the presence of adsorbed tais and oilsleft with the inateiial after burnn in two alternative ways.

ing. To the extent that these tarry bodies occur, the `carbon surfacesare not available for taking up oxygen. .All foi-ins of carbon areconductive for the electric current but again, to the extent; that theseadsorbed matters occur, conductivity is lessened and partitailarly "withUranulated masses. In the orilinai'y type oiF carbon which has beenproposed for use as an air depolarizing electrode, these tarry inattersreferred to exist to a considerable extent and experience has shown thatair depolarization properties, while existing, are `not suflicieiit forany practical purpose. On the other hand, an extreniely clean carbon,that' is, a `carbon which has been ignited under inild oxidizingu;-conditions so that practically all of the tarry matters have been drivenout, has kgood depolarizing properties and is highly conductive, even ingranular forni. But it has the disadvantage that adsorbed and absorbedwater reduces the oxygeii-adsorbiiig power." on which depolarizationdepends. Preparationsv of this character are lused for other purposesand are known commercial ly as activated carbons or decolorizingcarbons.

We have found, however, that ,it is possi.- ble to so prepare a carbonthat its oxygem adsorbiiig qualities are retained in a degree permittingits use as an efficient air depolan izing electrode, even after longperiods of exposure to the liquid elei'zti'olyte in a cell.` Ve haveobtained a carbon which retains its high adsorbing power for oxygen forindetinite-periods While ininiersed in the electro lytc found in cellsof this type.

ln preparing` this carbon We may proceed An ordinary coiiiinercialdecolorizing carbon, such Darco, which has a high adsorptive capacityfor oxygen, and is readily wetted by water, may be treated with a dilutesolution of an oil, such as iiiineral lubricating oil, in a volatilesolvent,` such as carbon tetrachlorid. The volatile solvent dilutes thefixed oil and allows convenient uniforni incorporation of the proportionof fixed oil We desire to retain in the carbon. After iiicorlioration`rthe volatile solvent is allowed to evaporate, leaving a sinall amount oflubricating' oil in or on the surface of the carbon. We have found thatlin the presence of this small aniount of oil, which is probably alladsorbed, aqueous liquids no longer exert a displacing e'ect on adsorbedoxygen.v The ad.-

sorbed film is or' practically molecular thickness, and is present tosuch a slight extent Vthat it does not interfere with the-.gasn yadsorbing properties of the material.` To,

gases, it is quite pervious. l

, In one specific embodiment of ourinvention, we treat a suitablequantity, say 6() parts by weight, of a'commercial" activated carbon,vsuch asDarco, 'with l5 parts by weight of a mineral oildiluted orthinned by the addition of 120' parts by weight of a diluent such ,ascarbon tetrachloride. As the mineral oil, an asphaltic base oil havingviscosityfrange of 90 to 100 is useful'. The carbon` is immersed orsoaked in the diluted oil until the oil" solution is substantiallywashing the carbon with a volatile solvent,

such as benzol', lgasoline,carbon tetrachlorid, etc. so as Vtoisc-extract most oi' the oil and to get a uniform distribution' oi" thesmall re sid'ual amount of oil left throughout the car- `bon mass. jWashing is not conducted to suchan` extent that .the last traces oflubrileating oil are removed.

Y This carbon so prepared hasr unusual properties. yWhereas ordinary,activated carbon'rapidly absorbs water', and its oxygen adsorbingqualities are thereby lessened,the

new carbon, possessing asmall amount oi adsorbed fixed oil, not readilywet by water, whereas the same carbon in an untreatedform is wet atonce. is wet by water or aqueouselectrolytes to a sufficient extent togive tree conductivitj.,rv when the material is used as anv electrode;but it does not absorb and adsorb water with the readiness oi".untreated carbon. The oile'd7 carbonhas not lost its eiiiciency,liowever,vtor adsorbing oxygen from the air. As an yelectrode in a cell,it exhibits depolarizing activity, not alone when first used, but

throughout the. life of the cell, provided it has an extension into theair. In some way, the presence of the adsorbed oil provides or permitsan avenue for the translocaticnjof adsorbed aerial oxygen from the point'where' it is taken up from the air to a point in contact' with theelectrolyte where 'the actual depolarization. occurs.

The new type of'carbon is particularly advantageous for use in the typeor cell em- The new carbon ployingan electrolyte of caustic sodasolution and electrodes of amalgamated zinc.

Ai-n-algamated zinc is not attacked by alkali solutions, even on opencircuit, toan material extent. Cells of this type are or inarilyemployed with'copper oxid as a depolarizer. .Such cells, however, giverather a low steady voltage and are not well `adapted to open circuit.On open circuit, the lslight solubility of coppervoxid incaustic alkalisolution causes, in time, a migration of copper to the zinc andconsequent local action. With the new depolarizing element, the steadyvoltage is approximately that corresponding to' aerial oxidation ofzinc, namely, about y 1.25 and there is practicallyno local action,

even on long-continued open circuit.

In cel-ls with an alkaline electrolyte, suchy asthe ordinary copper oxidtype ofcell, it

is custoniary to use a iloating layer of oil to `restrict Vevaporationand prevent encrustatlon or salines. In the present type of cell,

we can use oil also for the same purposes;

but in order to avoid this oil gaining access l Figure l is aview invertical section withv certain parts in elevation and certain other patsbroken away vto show the structure; an A Figure 2 is a similar view ofation employing feed mechanism to maintain constant feed of electrolyte.

Referring first to the structure shown in of any convenientnon-conductive material, such as glass, ceramic material, etc. A glass jar is shown. It is provided with cover 2 of porcelain, glass orV otherinsulating material, closing it at the top and supporting the cellelements. The closure'is not absolutel tight, since with hermeticsealing the cel would go out of operation. shown, however, that theamount of air leakage occurring with an ordinarilyk loose cover isusually enough to keep the oxygen in the contained atmospherereplenished toa suiieient extent' for the present purposes.` In ythisembodiment of my invention, the self-depolarizing negative element iscomposedv of a perforated, annular, metal element 8 containing a body ofed carbon 4. It is/desirable t at the granular mass in the basket 3 beput under a slight pressure to improve granule-to-granule conductivityand facilitate oxygen passage. Increased conductivity due to pressureconmodifica-v` Experience has;

Fig. l, element l is an ordinary battery jar p. j

. may be ofperforated sheet iron. As shown,

y air to enter the cell.

it will be notedthat the metal sleeve is not perforated at A.lmperforate metal extends above and below the normal level of a floatingoil seal 5 and prevents direct accessof the oil to the carbon. Above Athere are perfor-ations to allow the air in the ytop of the cell freeaccess to the carbon and below A the metal is again perforated to allowfree communication of the electrolyte with the carbon. The granularcarbon may be molded into shape with `a suitable binder and the basket 3is not then necessary, provided means are employed to prevent contact ofthe floatin oil seal 5 with the carbon electrode. Suc means may comprisea` sleeve of suitable material surrounding the electrode and positionedon the electrode where contact with the oil layer would normally occur.The Width of the sleeve should not be `much greater than the thicknessof the oil layer. Surrounding the negative electrode is posi tiveelement 6 oit zinein the form of an annular sleeve supported on aporcelain or hard rubber element 7. To it is connected insulated leadingwire 8 passing through a hole inthe cover. This hole is preferably madeslightly larger in diameterthan the conducting wire which passes throughit in order to provide positive means `to permit The electrical elementsare shown as supported lby an axially disposedrod-Q passing through theassemblage and carrying nut 10'at its base. At the top it passes throughlock nut 11. Washers 12 and wing nut 13, disposed on the rodA 9, serveas a means for obtaining an electrical-connection. The rod 9 may be madeof any suitable metal, such as copper, yto serve as a conductor to thenegative electrodey 1 The cell contains electrolyte 14 which may be anyusual type of caustic soda or caustic` potash solution. A 20 per centsolution of caustic soda is convenient ln the structure just described,reliance for depolarization is placed on the oxygen adsorbed by theupperlevels of the mass of carbon granules 3 and ltransferreddownwardly. Oxygen is supplied to the carbon by the air in the top ofthe cell. For replenishment of oxygen in this atmosphere, reliance isplaced on diffusion through the loose joints, suchas that around theinsulated wire, that between the cover and the top of the jar, etc.Sometimes we supplement these leakages with orifices in the cover (notshown). With inward diffusion of air, however, there is also outwarddiffusion. oit water from the moist carbon at the top of the electrode.The floating oil does not, of course, ob'viate this source of loss ofwater.

In the type of cell shown in Fig. 2, we employ means for replenishingthe evaporation of water and. to this end, we use a special type ofcover. The cell of this ligure is bet-- ter adapted for heavy duty thanthat of Fig. 1J since freer access of air maybe provided. This isadvantageous, since the amperage which can be delivered is proportionateto the amount ofoxygen adsorbed by the carbon surfaces. In the structureof Fig. 2, the several elements are mostly the same as in Fig. 1, and inthat event bear `the same reference numerals. It will be noted, however,that the cover 15 is entirely different. ltis made hollow to containabody of water 16. yOpening 17 closed by cork 18,.allows replenishmentof this body of water. From the cover depends outlet 19, depending to apoint below the normal liquid level of the cell. It acts as what issometimes known as -a bird fountain feed, replenishing the electrolytewhen its volume diminishes by evaporation. i

The particular cover l5 described has water replenishing means integralwith it as shown. If desired an ordinary cover, such as the one shown inFigi may be used. the water evaporated from the cell being continuouslyreplaced by the use of inverted water-filled bottles disposed above thecover and l'iavingtheir necks projecting through thecover andterminating below thesurface of the electrolyte. Such analternativearrangement does not possessthe simplicity7 and convenienceof the integral cover shown lin Fig. Q. `but the alternative arrangementmay be used.

What we claim is 1. .A self-depolarizing primary` cell having anelectrolyte of caustic alkaliy and a negative element of activatedcarbon, said element extending above the normal electrolyte level.

Q. A self-depolarizing primary cell having an electrolyte of causticalkali and a negative element of activated carbon, said elementextending above the normal electrolyte level and the surfaces of saidactivated carbon carrying a small amount of adsorbed oil. y

3. A self-depolarizing primary cell having an electrolyte of causticalkali and a negative element ofactivated carbon, said elementeX-tending above the normal electrolyte level, a floating layer yof oil onsaid electrolyte and means for preventing contact of said layer and saidcarbon. l

4. In an air-depolarized primary cell comprising a negative element oftreated acti- `vated carbon, having an adsorption power o particles .ofactivated carbon, a container for the carbon constructed of materialnor'- mallyimpervions to air `and to the electrolyte and havingpertorations,formed below the normal electrolyte level to permit accessof electrolyte to the carbon, and also perforations above the normalelectrolyte level to permit'y access oit air to the carbon, with anintermediate imperi'orate,portion and a prof,

tective layer of oil adapted to be disposed on the surface of theelectrolyte but maintained cao ontot' contact' with the carbon by meansci? said immediate imperlorate portion ot' the container. n y v 1 v wy6. A primary cell comprisingYa,l battery jar adapted to receive anelectrolyte,a cover for the jarA adapted to .lit loosely thereon, a rodextendingl through the cover within thc jar, adonble walled ycontainer'or' material,-

impervious to electrolyte supported oirtlie rod,"having perit'orationsboth above and below the normal level-'of the electrolyteto permit theaccess of air and o'lelectrolyte to corresponding portions of theinterior ot' the container with an .intermediate in'ipern forateportion, activated carbon Within the container,ysaid carbon being coatedwith a.

small amount of oil, a supporting member mounted Within the 3er by meansoi.' the rod,

and a metallic electrode disposed on the sup port circnmferentiallyaround the container. 7. Afprimary cell ot the air depolarized typecomprising. a battery jar adapted to receive an electrolyte, a coveradapted to lit loosely on the jar4 and permit accessot air, a containerfor an electrode depending from the cover, Asaidcontainer beingcontinuous and impermeable to fluids adjacent'the nor- .mal electrolytelevel. said container having perforations formed both-above and belowtbe normal electrolyte level to permittlie ace cess of airandielectrolyte therewithm, acti-- lvated carbonxdisposed Within. thecontainer,

means attached to the container ior support-- ing an electrode, andmeans for supplying liquidto the to compensate vfor losses o't theelectrolyte occuring through evaporation. v

8. A primary cell ofthe air depolarized type comprising a battery jaradaptedto receive anelectrolyte and electrodes, one of said electrodesbeinfr "formed o a plurality of particlesof activated` carbon, a metalcontainer for the carbon having peii`orations `formed belovv ther normalelectrolyte level to permit access of electrolyte to the carbon, andalso perforations above the non mal electrolyte level to permit accessof air to the carbon, Witlr an intern'iediate 1mperforate portion and aprotective layer of oil adapted to be disposed on thesurface ot theelectrolyte but n'iaintained out ol Contact with the carbon by meansoil? said immediate impert'orate portion of the container. i 9'. Aprimary cell 'of ythe air depolarized typeV comprising a battery jaradapted to re-` ceive an electrolyte and electrodes, one! of saidelectrodes being-'formed of a plurality. of particles of activatedcarbon, an electrically conductive container for the carbon` made otmaterial imperviousto electrolyte, said container e having `perforationsyformed below thenormal electrolyte level.z to permit Vaccessotelectrolyte to the carbon, and also .perforations above/they normalvelectrolyte level to permit access of air to the carbon,

with an l intermediate -imperlforate portion and aprotective layerof-.oil adapted .to be disposed on the surface otthe electrolyte butmaintained `out of contact ,with` the .can

bon by means ot said immediate imperforate portionoi? the container. l il0. A rnnar .cell com rismv a contain er,electrolyte disposed therein,layer oi. oil 'on the surince of. the electrolyteand sealing the samefrom cont-act Witlrair, ade-1 polarizing element projecting through saidlayer ot oil into the air and electrolyte, and means protecting thedepolarizingelement from contactiswitli theioil.

y 11. A primary i cell comprising Va contamer, electrolyte disposedtherein, a layer oit' oil on the surface ott the electrolyteyand sealingthe Asamelrom Contact With'l air, a depolarizingelement projecting nthrough said layer oi oil into the air and electrolyte,

yand a. protective sleeve positioned around the depolarizing element toprevent contact ort said'ioil'and depolarizing elenient, said Sleevevprojecting y,into tlieelectrolyte and the air. Y

l2. A voltaic cell oi: the air; depola-rizer type comprising," acontainer, a cover therefor, rin-electrolyte Within the container,elec-` trodes depending from said cover `into said electrolyte,.aprotective seal on the surface of the electrolyte, and a sleevesurrounding oneol said electrodes to prevent contactzof the protectiveseal and the electrode, y,

13.A voltaicvcell comprising' a container, a cover therefor,janelectrolytewithin the. container, positive and negative electrodes'depending from the cover to the electhe cover Within said container,one of said electrodes being'a depolarizing electrode, an

electrolyte in the container' contacting with the electrodes, a layer of-oil on the elec-- trolytel preventing evaporation therefrom, va.

trede projecting beyond said cover into the air and thereby providingmea-ns for exchange between said electrolyte und the zur,

said sleeve extending above and below the surface of the layer of oil,enel means on the under 51de of sald eover colnmunlcatmg with saidrecess and. electrolyte `to permit l0 of the flow of liquid from therecess to the container.

In Witness whereof We have hereunto signed our' names at Waterbury,Connecticut, `this 4th day of October, 1926.

MARTIN L. MARTUS. EDMUND H. BECKER.

